People of all ages enjoy coloring, paint by numbers, and other forms of entertainment having line drawings as an essential element. Digital line drawings are digital images that are similar in appearance to traditional line drawings. Digital line drawings may be characterized by a substantially bimodal distribution of pixel values, with pixels close in value to one mode being associated with the lines and pixels close to the other mode forming the background.
Universal adoption of digital cameras, as dedicated gadgets or as incorporated within multi-function devices such as cellular phones, has led to widespread availability of digital images. Consumers may wish to convert their digital images into digital line drawings to allow painting or coloring of personal subject matter. The ability to capture memories or special events in this way makes for a more interesting and engaging experience and end product, especially for children.
Straightforward and simple methods of producing digital line drawings from digital images involve application of an edge detection operator to the digital image, followed by a threshold operation. These steps may be effectively carried out in many popular image editing computer programs such as Adobe Photoshop™. Application of such straightforward methods, however, can produce digital line drawings with noise, loss of key elements from the scene, or excessive detail that limits the usefulness of the result for coloring or painting purposes. The present invention improves upon these simple methods and may reduce noise, eliminate excessive detail, and preserve scene elements that are essential for a good coloring page.
For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for an effective and efficient method to produce high quality digital drawings from digital images.